Multiple Audio Tracks in iMovie

Hello guys,

i'm using iMovie 10.0.9 on my MacBook Air mid 2012 running OSX Yosemite. I'm german so my english will not be perfect. :-)

I actually have two Questions:

1.)

I'm trying to edit a MP4 Movie File which has 2 language tracks. German and English. But iMovie always preselects the German one. Of course i google'd, but the most given answer is to delete one Track using Quicktime Pro. But i don't have QT Pro. Is there a way to select between multiple Audio Tracks in iMovie?

2.)

And my second Question is, is there a way to reunite seperated Audio and Video Parts in iMovie after editing them?

Background: I'm editing one part of a video, select it, seperate the Audio from the Video, put another Audio under the Video part, and now i always have to select both Audio and Video when i want to move it, or copy it to play it multiple times etc. is there a way to put Audio and Video together to one part again?